Beacon antenna system



June 19, 1962 c. LucANERA ETAL BEACON ANTENNA SYSTEM Filed Dec. 9, 1958 MOTOR A QWRYM W wf m TASC Nm? w E N V/ aMT mwKA. A fld M r. lwa wAM w?? V.. B

2 2 i 3 bz (w 2 sf c W W United States Patent O 3,040,319 BEACON ANTENNA SYSTEM Constantino Lucanera, Blauvelt, N.Y., and Frank E.

Kolinsky, Wanaque, and Ernest J. Annechiarico, Ramsey, NJ., assignors to International Telephone and Telegraph Corporation, Nntley, NJ., a corporation of Maryland Filed Dec. 9, 1958, Ser. No. 779,151 1 Claim. (Cl. 343-761) This nvention relates to beacon antenna's and more particularly to beacon antennas producing a rotating multilobed pattern of radiation in which the rotating lobes serve to modulate the carrier signal radiated in any given direction. The antenna system described in this nvention produces relatively constant percentage modulation of said carrier frequency up to high elevation angles.

In the past, beacon antennas have been employed to radiate a carrier frequency in a rotating multilobed pattern thereby producing carrier modulations in any given direction from which Vehicles having receiving equipment on board may determine their relative bearings to said beacon. One such beacon is described in Patent No. 2,836,820, of S. Pickles et al., filed January 4, 1955. The beacon antenna described in the Pickles patent consists, briefly, of a central vertically polarized radiator coupled to a transmission line with parasitic elements spaced for rotation about the central radiator. The rotation of these parasitic elements about the central radiator produces the rotating lobes in the pattern of radiation from the beacon, and these parasitic elements are essentially vertically arranged straight conducting members.

The use of parasitic elements to alter the directivity of an antenna, as in the Pickles patent, -is a well-known technique. In operation the parasitic element will intercept some of the energy radiated from a driven antenna element and then re-radiate it. The re-radiated energy combines with the energy radiated by the driven antenna element in such a way to modify the directional pattern of the driven element creating lobes in that directional pattern. The degree of modification depends upon the relative positions of the driven and parasitic elements, the magnitude of currents flowing in them and the relative phase of the currents. Parasitic elements increasing the gain of the driven antenna element in -the direction from the driven element to the parasitic element are termed directors while parasitic elements that increase the gain in the direction from the parasitic element to the driven element are called reflectors. It is also well known to the art that a parasitic element located a fixed distance from a driven element which is energized by a given frequency, can be caused to be a reflector or a director depending on its length. Consequently, lobes in the radiation pattern from a driven antenna element can be made more pronounced or less pronounced by altering the length of a parasitic element at a fiXed distance from the driven element.

In the past, the lobes in the radiation pattern from antennas, such as described in the Pickles patent, have been adjusted by altering the length of the parasitic elements. However, such alterations in the length of these parasitic elements also altered the coupling between the parasitic element and the central driven antenna elements,

thus changing the frequency response of the antenna system. These alterations in length have also caused the percentage of modulation of the carrier frequency to vary appreciably with increasing elevation angles so that the percentage of modulation does not remain constant as elevation angle increases. Obvously, in many instances, such changes in the coupling resulting in frequency response changes and changes in percentage modulation With elevation angle are undesirable, even though it is desired to alter the overall percentage modulation. In other instances, it may be desired to al-ter the frequency response of the antenna system vvithout changing the overall percentage modulation. Neither of these desired conditions can be achieved by altering the length of the parasitic elements in antenna systems, such as shown in the Pickles patent.

Therefore, it is a principal object of this nvention to provide a directional antenna system having none of the above-mentioned limitations.

It is another object to provide a directional antenna system in which the Shape of parasitic elements at fiXed positions may be altered to change frequency response and/or the ratio of the gain of the antenna in the direction of its lobes to its gain in directions between lobes, 'without altering said ratio at increased elevation angles.

It is another object to provide an improved beacon antenna having a rotating multilobed pattern of radiation employing parasitic elements which may be altered in size and shape to increase or decrease antenna directivity without altering frequency respo-nse or percentage modulation of the carrier frequency at increased elevation angles.

It is another object to provide such a beacon antenna having low overall height including parasitic elements disposed for rotation about a central vertically polarized radiator in which said parasitic elements may be considerably longer than said overall height.

It is a feature of this nvention to provide an antenna having a directional radiation pattern comprising central radiating elements and at least one loop parasitic element disposed to intercept radiation from said central element thereby creating the directional pattern.

It is another feature to provide a beacon antenna having a rotating directional radiation pattern comprising a vertically polarized central radiator, a plurality of loop parasitic elements disposed at equal distance from said Vertical radiator, each lying substantially in a plane perpendicular to radial lines from said Vertical radiator.

It is a feature of one embodiment of this nvention to provide an antenna system employing a Vertical arrangement of said loop parasitic elements for rotation abou-t a multiple element Vertical radiator energized by a carrier frequency signal to create a fundamental lobe in the pattern of carrier frequency radiation, the length of each of said loops being fixed to achieve a given percentage modulation of said carrier frequency in any given direction and the height of each of said loops being fixed to tune said system and maintain percent modulation Constant even at increased angles of elevation, and -to employ other parasitic radiators disposed at a greater radial distance from said central radiator for rotation thereabout to create harmonic lobes in the pattern of carrier frequency radiation energizing the system.

It is a feature of another embodiment of this invention to provide an antenna system employing a V-shaped parasitic element disposed for rotation about a vertically polarized central radiator energized by a carrier-frequency signal with a plurality of loop parasitic elements disposed at a greater radial distance for rotation about said central radiator, the length of each of said loops being fixed to achieve a given percentage modulation of said carrier frequency in any given direction and the height of each of said loops being fixed to tune said system and maintain percent modulation constant even at increased angles of elevation, said V-type element producing a fundamental in the radiation pattern and said lobe elements producing harmonic lobes, the height of the system being preferably less than the length of one of the loop elem-ents.

The foregoing and other objects and features of this invention and the manner of attaining them Will become more apparent and the invention itself will be best understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, comprising FIGS. l, 2 and 3, wherein:

FIG. l is a pictorial cutaway view of a beacon antenna producing a rotating multilobed pattern having a fundamental and ninth harmonic lobes;

FIG. 2 is a pictorial cutaway view of a simple beacon antenna having minimum overall height for producing a rotating pattern of radiation having a fundamental lobe and harmonic lobes; and

FIG. 3 is a detailed cutaway view showing the central radiator and disposition of lobe parasitic elements of the antenna system shown in FIG. 1.

Turning first to FIG. 1 there is shown the top of a central vertically polarized radiator 1. This central radiator is shown in more metail in FIG. 3 and is preferably constructed and energized, as described in Patent No. 2,762,- 045 of G. Stavis et al., filed October 8, 1952. Concentric with this central radiator is a dielectric cylinder 2 for supporting conductive loops 3 and 4 and 5, as well as conductive spoiler plate 6. These conductive loops serve as parasitic elements altering the directivity of radiation from central radiator 1. A second dielectric cylinder 7 also concentric With central radiator 1 serves to support other parasitic elements such as straight elements 8, 9 and 10. As shown in the figure, straight elements 8, 9 and 10 are each orientated in cylinder 7 on different center lines circumferental with cylinder 7. These different center lines are lines 11, 12 and 13, respectively. Numerous other straight parasitic elements, such as for example, eight other elements are also located on these center lines. The preferred orientation of the center lines 11, 12 and 13 upon which the straight parasitic elements are located, with regard to the location of loop parasitic elements 3, 4 and 5, respectively, are as follows: Center line 11 forms a plane which bisects conductive loop 3 while line 12 forms a plane which bisects conductive loop 4 and line 13 forms a plane which bisects conductive loop 5. The distance between centers of conductive lobes 3 and 4 is preferably about one wavelength of the center frequency of the band over which the antenna system is operated and the distance between centers of loops 4 and is also one wavelength.

Dielectric cylinders 2 and 7 are supported by counterpoise surface 14 which may be coupled through suitable means to the outer conductor 15 of transmission line 16 conducting carrier frequency signals. The inner conductor 17 of transmission line 16 is coupled to central radiator 1, as shown in FIG. 3. Motor 18 serves to rotate surface 14 about central radiator 1 and for this purpose gear box 19 and gears 20 couple the output of motor 18 to an extension of surface 14. Consequently, the multilobed pattern of carrier frequency radiation created by the central radiator and the parasitic loops and straight members is rotated. This rotation causes the carrier frequency to be modulated at modulating frequencies proportional to the rate of rotation and number of lobes in said pattern. In this embodiment, these modulating frequencies are a fundamental, resulting from rotations of the fundamental lobe created by the loop parasitic elements and a harmonic, resulting from rotations of the harmionic lobes created by the straight parasitic elements.

In operation Spoiler plate 6 serves to refiect radiation emanating from the upper part of the central radiator which is directed by conductive loop 3 and when reflected, this radiation adds to the gain of the system at high elevation angles. Loop elements 3, 4 and 5 are elliptical, as shown in the figure. However, these elements may be loops of any shape and may be open loops rather than closed loops. If these elements are open loops, the open ends are preferably separated only a few tenths of a wavelength. Some of the advantages of employing these loops are that the height of a loop may be fixed while its length may be altered considerably. Consequently, by fixing the height of the loops, the frequency response of the antenna system remains fixed and by altering the length of the loops, the percentage of fundamental modulation of the carrier frequency radiated by element 1 may be altered and this alteration in fundamental carrier frequency modulation may remain constant up to high elevation angles. The distance from center line 13, upon which are located a number of straight parasitic elements to counterpoise surface 14, is preferably five-fourths of a wavelength while the diameter of spoiler plate 6 is preferably three halves of a wavelength when the diameter of cylinder 7 is three wavelengths.

Turning next to FIG. 2 there is shown another embodiment of this invention depicting a beacon antenna having an overall height of approximately one wavelength, and consisting of a vertically polarized radiator 21 coupled to the central element 22 of coaxial transmission line 23. The outer element 24 of coaxial line 23 is coupled by some suitable means to conductive plate 25, which acts as a counterpoise surface for the system. Disposed concentric with element 21 and supported by plate 25 are dielectric cylinders 26 and 27. Cylinder 26 serves to support V-shaped parasitic element 28 while cylinder 27 supports a number of loop parasitic elements., such as element 29. Motor 30 drives plate 25 in rotation about central radiator 21 through suitable mechanical coupling consisting of, for example, gear box 31 and gears 32 coupled to an extension of plate 25.

A beacon antenna, such as shown in FIG. 2, has a preferred overall height of one wavelength or less with a diameter of approximately three wavelengths. Such an antenna is most useful where space and weight of antenna structure must be minimized, such as in certain Vehicles like a submarine or aircraft. Here again, the loop parasitic elements such as element 29 may have a fixed minimum height and their length may be varied over a wide range to increase or decrease percentage modulation in carrier frequency without appreciably eifecting the tuning of the antenna system and without appreciably eifecting changes in percentage modulation with elevation angle.

While there is described above specific embodiments of this invention, it should be apparent that lobe parasitic elements having shapes other than round or oval may be employed, as described, without deviating from the spirit and scope of the invention and that numerous types of open loop parasitic elements having openings within the limitations mentioned above could be employed in the manner described in place of those shown without deviating from the spirit and scope of the invention as encompassed by the following claim.

We claim:

An antenna system having a rotating radiation pattern with a fundamental and harmonic lobes, said fundamental lobe being created by a first group of parasitic elements and said harmonic lobes being created by a second group of parasitic elements comprising a central vertically polarized radiator having an axis and consisting of a plurality of biconical elements arranged in a Vertical manner along said aXis, a plurality of Curved loop parasitic elements to create said fundamental lobe disposed one above another on a cylindrical surface concentric with said central radiator each said loop parasitic element being curved about said axis with all portions of said parasitic element being at the same radial distance from said axis Whereby the radiation from all points of any one of said loop parasitic elements is in phase and a plurality of other parasitic elements disposed on another cylindrical surface concentric with said central radiator, said second group of elements being arranged in sub-groups in different horizontal planes, each plane bisecting a different one of said loop parasitic elements each of said planes being separated from an adjacent plane by a distance of substantially one wavelength, said cylindrical surfaces being supported by rotatable means and drive means for rotating said surfaces References Cited in the file of this patent UNITED STATES PATENT S 2,l69,553 Bruce Aug. 15, 1939 2,480,181 Breen et al Aug. 30, 1949 2,60l,610 Hatch et al June 24, 1952 2,702,858 Foster Feb. 22, 1955 2,836,820 Pickles et al May 27, 1958 2,866,194 Stavis et al Dec. 23, 1958 2,912,693 Lucanera et al Nov` 10, 1959 

